Search Results for: meiosis 1
Characteristics and Traits
Learning Outcomes Understand how the inheritance of a genotype generates a phenotype The seven characteristics that Mendel evaluated in his pea plants were each expressed as one of two versions, or traits. The physical expression of characteristics is accomplished through the expression of genes carried on chromosomes. The genetic makeup of peas consists of two Read more »
Laws of Inheritance
Learning Outcomes Apply the law of segregation Apply the law of independent assortment Mendel generalized the results of his pea-plant experiments into four postulates, some of which are sometimes called “laws,” that describe the basis of dominant and recessive inheritance in diploid organisms. As you will learn, more complex extensions of Mendelism exist that do Read more »
Non-Mendelian Inheritance
Learning Outcomes Explain how a trait with incomplete dominance will appear in a population Explain how a trait with codominant inheritance will appear in a population Explain how a trait with sex-linkage will appear in a population Incomplete Dominance Mendel’s results, that traits are inherited as dominant and recessive pairs, contradicted the view at that Read more »
Mendel’s Experiments and Heredity
Learning Outcomes Describe Mendel’s study of garden peas and heredity Genetics is the study of heredity. Johann Gregor Mendel set the framework for genetics long before chromosomes or genes had been identified, at a time when meiosis was not well understood. Mendel selected a simple biological system and conducted methodical, quantitative analyses using large sample Read more »
Common Conditions
Learning Outcomes Identify common errors that can create an abnormal karyotype Identify syndromes that result from a significant change in chromosome number Of all of the chromosomal conditions, abnormalities in chromosome number are the most obviously identifiable from a karyogram. Conditions of chromosome number include the duplication or loss of entire chromosomes, as well as changes in Read more »
Chromosomal Structural Rearrangements
Learning Outcomes Understand the impact of translocation between non-homologous chromosomes during meiosis or mitosis Cytologists have characterized numerous structural rearrangements in chromosomes, but chromosome inversions and translocations are the most common. Both are identified during meiosis by the adaptive pairing of rearranged chromosomes with their former homologs to maintain appropriate gene alignment. If the genes Read more »
Sexual Reproduction
Learning Outcomes Understand how sexual reproduction leads to different sexual life cycles Sexual reproduction was an early evolutionary innovation after the appearance of eukaryotic cells. It appears to have been very successful because most eukaryotes are able to reproduce sexually, and in many animals, it is the only mode of reproduction. And yet, scientists recognize Read more »
Putting It Together: Cell Division
Mitosis and meiosis are both forms of division of the nucleus in eukaryotic cells. They share some similarities, but also exhibit distinct differences that lead to very different outcomes (Figure 1 and Table 1). Mitosis is a single nuclear division that results in two nuclei that are usually partitioned into two new cells. The nuclei Read more »
Why It Matters: Cell Division
Why describe and explain the various stages of cell division? Cell division is key to life: from the moment we are first conceived, we are continually changing and growing. In order for our bodies to grow and develop, they must produce new cells—and allow for the death of old cells. Cell division is also an essential component Read more »
